Muzhuping landslide, 700 million m3 in volume, which occurred in the Shuibuya Reservoir area on May 10, 2007, is one of the serious landslide disasters in this area after second stage impounding. And it caused a serious loss of property. According to the on the-spot survey on this landslide, the paper introduces the geological background in landslide area and the geologic and geomorphic characteristics. By means of the landslide stability calculation, it is considered that the occurrence of Muzhuping landslide was the union action result of inner and outer causes. The front area of the landslide was cut by the branch of Qingjiang River, which offered a free face. And the thin layer limestone and quaternary alluvial purple soil easily inclined to slide. The result shows that the vulnerably geological structure of landslide body, concentrated rainfall and reservoir impoundment caused this landslide.